For example, in a semiconductor integrated circuit, an oscillator has been widely used as a signal source which sets a reference frequency. However, the oscillation frequency of the oscillator varies depending on the temperature. Therefore, the oscillation frequency of the oscillator is corrected according to a temperature variation. The temperature characteristics of the oscillator are measured in order to correct the oscillation frequency of the oscillator. At that time, when the entire IC chip having the oscillator incorporated thereinto is heated, it takes a long time for the temperature to be stabilized. As a result, it takes a long time to measure the temperature characteristics.